There needs to be a term for someone that ignores everything like a sieve, but manages to catch the smallest of morsels off which to launch a fallacious diatribe, as though nothing else happened.

They’re not.a.troll; they’re something quite different. A mix of insecurity, hyperfocusing, a tendency to exercise many argument fallacies, a resolve that can deny itself, no clear purpose in its behaviour beyond either “winning” or perhaps just seeking social interaction.

I’d go with “Teflon” because nothing sticks, but it doesn’t cover their wannabe polemicist nature.